In Busan, you can visit kasina in Gwangali. This is their website:
www.kasina.co.kr
They are located a short walk from Geumnyeonsan subway near Gwangali Beach. Walk down from the subway and trun right at the crossroads. Then walk about 100 meters and the shop is on your left.
Click on the link to see them on naver maps:
http://me2.do/5q2cBSC .
There are some other shops in the area that occasionally sell skateboards, but kasina people are skateboarders.
Once you have your board, you may find the following site useful:
http://www.skate-park.co.kr/
Hope it helps.

Kasina is a 'seasonal' skateboard store! with tempremental opening hours! Many a time I have trailed over there (with my Middle School son!) from Haeundae to find they were either closed or it was still snowboard season! Your best bet really is ordering online (my hubby gets all my son's stuff from America - the postage isn't bad at all). There is a decent skate store in Itaewon, Seoul. & one of the Korean skaters told my son there is a new skate shop in Nampodong called Ghost Town (I think thats the name). But we could never find it. 2 good skateparks in Gimhae. One near the airport, you can't miss it and one at Gimhae Stadium. Think there is a smaller one over by Ssasang? Never been. Nothing close to Haeundae!